Pheochromocytoma cells in vitro and in vivo may exhibit some phenotypic characteristics which are "appropriate" functions of normal chromaffin cells and others which are not expressed by normal chromaffin cells. The latter are generally highly differentiated functions characteristic of a variety of amine and peptide hormone-producing neural and endocrine cells from other parts of the body, rather than expressions of random genomic derepression. The molecular mechanisms which cause pheochromocytoma cells to exhibit aberrant characteristics selected from a finite repertoire of neuroendocrine functions, and the events which lead to expression of these characteristics in the course of neoplastic progression, are not known. Studies at the cellular level indicate that production of the peptide neurotensin (NT) and of catecholamine biosynthetic enzymes are regulated by corticosteroids and NGF in PC12 rat pheochromocytoma cells. NT is also present in human pheochromocytomas, but not in the normal rat or human adrenal in vitro. In these studies, we will focus on NT and catecholamine biosynthetic enzymes as models of "aberrant" and "appropriate" functional markers applicable to both human and rat pheochromocytomas, and we will extend our studies to the molecular level to investigate mechanisms involved in regulation of these markers. Using mRNA from PC12 cells as templates, we will construct and clone complimentary DNAs (cDNAs) encoding NT and catecholamine biosynthetic enzymes. These cDNAs will be used in hybridization assays to quantitate changes in specific mRNA levels in response to corticosteroids and NGF and to investigate the organization of the genes encoding NT and catecholamine biosynthetic enzymes. They will also permit us to determine the complete amino acid sequence of the NT precursor. We will concomitantly expand our studies at the cellular level, comparing mechanisms which regulate the synthesis, storage and secretion of NT and catecholamines in normal, hyperplastic and neoplastic chromaffin cells of humans and rats. These studies will shed light on mechanisms which determine normal neuroendocrine cell phenotype, and on ways in which normal regulation might become deranged during the development of neoplasia.